Features:1. Aluminum Alloy shell is precision machined, stable and durable for long time use.2. This is a 4X achromatic objective lens for biological microscope.3. It can eliminate unwanted reflections and increase contrast.4. Offers high quality observation without additional chromatic aberration, make image more clear.5. The Length of the objective lens is 30.5mm, easy to use.Specification:Item Type: Achromatic Objectives LensMaterial: Aluminum Alloy + Optical LensColor: As Pictures ShowMagnification: 4XTube Length: 160mm / 6.3inchConjugate Distance: 185 Cover-glass Thickness: 0.17mmObjective Lens Length: 30.5mmMounting Size: 20mmStandard RMS Thread)Item Size: 5 * 5 * 5cm / 2.0 * 2.0 * 2.0inchPackage Weight: Approx. 41gPackage List:1 * Achromatic Objectives Lens